Search results for "flagella"
showing 10 items of 61 documents
Hydrodynamics with spin in bacterial suspensions
2016
We describe a new kind of self-propelling motion of bacteria based on the cooperative action of rotating flagella on the surface of bacteria. Describing the ensemble of rotating flagella in the framework of the hydrodynamics with spin the reciprocal theorem of Stokesian hydrodynamics is generalized accordingly. The velocity of the self-propulsion is expressed in terms of the characteristics of the vector field of flagella orientation and it is shown that unusually high velocities of \textit{Thiovulum majus} bacteria may be explained by the cooperative action of the rotating flagella. The expressions obtained enable us to estimate the torque created by the rotary motors of the bacterium and …
Identification of the ectosymbiotic bacteria of Mixotricha paradoxa involved in movement symbiosis
2003
Mixotricha paradoxa, a trichomonad from the hindgut of the Australian termite Mastotermes darwiniensis Froggatt, is a rare example of a movement symbiosis between eukaryotic and prokaryotic microorganisms. The surface of Mixotricha paradoxa is covered with spirochaetes and a rod-shaped bacterium. The four flagella at the anterior end seem only to alter the direction of movement, while the ectosymbiotic spirochaetes propel the flagellate cells. Based on a 16S rDNA sequence analysis after a semi-specific PCR, and subsequent fluorescence in situ hybridization applying helper oligonucleotides and a denaturing step of the 16S rRNA, three different spirochaete clones could be clearly identified o…
Immunoelectron Microscopy of Vesicle Transport to the Primary Cilium of Photoreceptor Cells
2009
Cilia are organelles of high structural complexity. Since the biosynthetic machinery is absent from cilia all their molecular components must be synthesized in organelles of the cytoplasm and subsequently transported to the cilium. Ciliary cargos are thought to be translocated in the membrane of transport vesicles or association with these vesicles to the base of the cilium where the vesicles fuse with the periciliary target membrane for further delivery of their cargo into the ciliary compartment by the intraflagellar transport (IFT). Here we describe a modified preembedding labeling method as an alternative technique to conventional postembedding methods eligible for analyses of ciliary c…
Intraflagellar transport protein 172 is essential for primary cilia formation and plays a vital role in patterning the mammalian brain
2008
AbstractIFT172, also known as Selective Lim-domain Binding protein (SLB), is a component of the intraflagellar transport (IFT) complex. In order to evaluate the biological role of the Ift172 gene, we generated a loss-of-function mutation in the mouse. The resulting Slb mutant embryos die between E12.5 and 13.0, and exhibit severe cranio-facial malformations, failure to close the cranial neural tube, holoprosencephaly, heart edema and extensive hemorrhages. Cilia outgrowth in cells of the neuroepithelium is initiated but the axonemes are severely truncated and do not contain visible microtubules. Morphological and molecular analyses revealed a global brain-patterning defect along the dorsal–…
Ultrastructure of Joenoides intermedia (Grassé 1952), a symbiotic parabasalid flagellate of Hodotermes mossambicus, and its comparison with other joe…
2003
Light and electron microscopy confirms the validity of the genus Joenoides. The cell is organised like other joeniids with a triangular flagellar area of about two thousand flagella/basal bodies and three privileged basal bodies located apart at the anterior corner of the flagellar area. Characteristically, the two parabasal fibres attached to the basal body #2 are very large and composed of striated subfibres that spread in the cytoplasm, where they sustain Golgi bodies. The flagellar area is surrounded by the axostylar capitulum, which is underlain by a thick layer of preaxostylar fibres, a very strongly amplified component in this species. The axostylar trunk is composed of a bundle of m…
Bacteria of the Genus Roseobacter Associated with the Toxic Dinoflagellate Prorocentrum lima
1998
The dinoflagellate Prorocentrum lima is known to produce diarrhetic shellfish poisons. However, it is yet unclear if the dinoflagellates themselves or the bacteria associated with them produce the toxins. Here we analyze the toxicity as well as the spectrum of bacteria in two cultures of P. lima, namely P. lima-SY and P. lima-ST, which initially derived from the same P. lima strain PL2V. Toxicity tests, applying the Artemia bioassay revealed in both cultures high levels of toxins. The bacteria, associated with the two cultures, were identified by PCR/nucleotide sequence analysis of the 16S rRNA gene. From cultures of P. lima-SY the dominant sequence was found to share a 93.7% similarity wit…
REINSTATEMENT OF THE DINOFLAGELLATE GENUS Tripos TO REPLACE Neoceratium, MARINE SPECIES OF Ceratium (DINOPHYCEAE, ALVEOLATA)
2013
Morphological and molecular data support the split at the genus level of the marine and freshwater species of the dinoflagellate Ceratium (Gonyaulacales, Dinophyceae). A new genus name Neoceratium F. Gomez, D. Moreira & P. Lopez-Garcia was proposed for the marine species. However, it is considered illegitimate (type species is type of Biceratium Vanhoffen), and the nomenclatural priority is here given for the genus Tripos Bory (type species Tripos muelleri ) which replaces Neoceratium . New combinations are proposed for the existing names of species and infraspecific taxa. Reinstalacion del genero de dinoflagelados Tripos para reemplazar a Neoceratium , especies marinas de Ceratium (Dinophy…
Influence of dissolved organic matter from terrestrial origin on the changes of dinoflagellate species composition in the Gulf of Riga, Baltic Sea
2004
A mesocosm experiment was used to investigate the effect of terrestrial-origin dissolved organic matter (DOM) on the development of dinoflagellates in natural summer phytoplankton from the Gulf of Riga. Seawater was collected in the central part of the Gulf of Riga and at the entrance of the Gulf in June 1999. DOM was extracted from Parnu River water by use of tangential ultrafiltration. Experimental series were enriched with DOM, DOM in combination with nitrate and phosphate, and only with inorganic nutrients. Enrichments were added in ranges of their natural concentrations. Dinophysis acuminata, Protoperidinium brevipes and Gymnodinium spp. were dominant species in the initial dinoflagell…
TEM observations on symbionts ofJoenia annectens(Flagellata Hypermastigida)
2001
Transmission electron microscopy was used to evaluate the ultrastructural morphology of some other symbiotic prokaryotes of Joenia annectens, an intestinal flagellate of the termite Kalotermes flavicollis. Three morphotypes are predominant and recognizable from their morphological characteristics. One morphotype is represented by spirochaetes that are mainly external and cover the flagellate, helping its movement. Rod-shaped bacteria, which represent the second morphotype, are also attached to the surface among the spirochaetes. Rod-shaped bacteria and some spirochaetes may enter the cell surface of Joenia annectens as a consequence of phagocytosis, remaining enclosed in an envelope of plas…
Ultrastructure and freeze-fracture studies of the thylakoids ofMantoniella squamata (Prasinophyceae)
1988
The ultrastructure and the supramolecular organization of the thylakoids of the small green flagellate,Mantoniella squamata, were examined in thin sections and freeze-fracture preparations. The whole chloroplast is tightly packed with thylakoids, which show a pattern of meandering, branching and/or anastomosing membranes. In freeze-fracture preparations only two fracture-faces can be distinguished: the PF- and the EF-face. The PF-face has a much higher particle density than the EF-face (PF: 4086 particles/μm2; EF: 865 particles/μm2). The EF-face is not as uniform as the PF-face. The areas which are packed with particles probably correspond to closely appressed thylakoid regions or adhesive …